6 9 



MOUNTING AND LABELING. 



For the purpose of measuring cover-glasses two very convenient 

 cover-glass measures or cover-glass testers have been devised, one made 

 and furnished by Zeiss, Reichert, etc., in Europe, and the other, de- 

 vised by Edward Bausch and furnished by the Bausch and Lomb Opti- 

 cal Co. of Rochester, N. Y. With either of these the cleaned covers 

 may be very quickly and accurately measured. The different thick- 

 nesses can then be put into different boxes and properly labeled. 

 Unless one is striving for the most accurate possible results, cover- 

 glasses not varying more than T tts mm - ma Y be put in the same box. 

 For. example, if one takes ^ s mm. as a standard, covers varying yf^ 

 mm. on each side may be put into the same box. In this case the box 

 would contain covers of T W tW» t¥<f» tW an d tVst mm - 



Fig. 38. Cover-Glass Measurer (Edzvard Bausch). 



The cover-glass is placed in the notch between the two screws, and the 

 drum is turnea by the milled head at the right till the cover is in contact 

 with the screws. The thickness is then indicated by the knife edge on the 

 drum, and may be read off directly hi jjr$th mm. or 1 -^jjth inch. In 

 other columns is given the proper tube-length for various unadjustable ob- 

 jectives {\, \, \, and -j^, in.) made by the Bausch and Lomb Optical Co. 



